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CURLOPT_RESOLVER_START_FUNCTION(3) curl_easy_setopt options
CURLOPT_RESOLVER_START_FUNCTION - callback called before a new name
resolve is started
int resolver_start_cb(void *resolver_state, void *reserved, void *userdata);
CURLcode curl_easy_setopt(CURL *handle,
Pass a pointer to your callback function, which should match the
prototype shown above.
This callback function gets called by libcurl every time before a new
resolve request is started.
resolver_state points to a backend-specific resolver state. Currently
only the ares resolver backend has a resolver state. It can be used to
set up any desired option on the ares channel before it's used, for
example setting up socket callback options.
reserved is reserved.
userdata is the user pointer set with the
The callback must return 0 on success. Returning a non-zero value will
cause the resolve to fail.
NULL (No callback)
static int resolver_start_cb(void *resolver_state, void *reserved,
printf("Received resolver_state=%p userdata=%p\n",
CURL *curl = curl_easy_init();
curl_easy_setopt(curl, CURLOPT_RESOLVER_START_FUNCTION, resolver_start_cb);
curl_easy_setopt(curl, CURLOPT_RESOLVER_START_DATA, curl);
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
Added in 7.59.0
libcurl 7.87.0 May 17, 2022